How Do We Know How Old the Sun really is and do We really Know its Ultimate fate ??

[Vertigo]

Not really. The equation simply describes the fundamental equivalence between mass and energy. It is basic and it always applies to everything.

In fact come to think about it, is it not really describing the ultimate potential energy? It's certainly not describing kinetic energy as it does not involve the velocity of the mass and kinetic energy is surely a function of mass and (relative) velocity? Maybe I'm wrong but that's how I understood it.

 

[hitmouse]

In fact come to think about it, is it not really describing the ultimate potential energy? It's certainly not describing kinetic energy as it does not involve the velocity of the mass and kinetic energy is surely a function of mass and (relative) velocity? Maybe I'm wrong but that's how I understood it.

Don't confuse C with kinetic energy or velocity. It is simply a universal constant. E is proportional to M, but e=mc^2. Think about the energy released in a nuclear reaction.

 

[Vertigo]

Don't confuse C with kinetic energy or velocity. It is simply a universal constant. E is proportional to M, but e=mc^2. Think about the energy released in a nuclear reaction.

No, that's why I said it doesn't describe kinetic energy, what it describes is the potential energy available if it's completely converted to energy.

 

[Venusian Broon]

In fact come to think about it, is it not really describing the ultimate potential energy? It's certainly not describing kinetic energy as it does not involve the velocity of the mass and kinetic energy is surely a function of mass and (relative) velocity? Maybe I'm wrong but that's how I understood it.

Potential energy is the energy of a particle that it possesses because of it's position relative to other particles. Usually we think of a particle and it's relationship to a field, where the field has been generated by another particle. e.g. gravitational field and mass.

E=mc^2 is a truncated term that comes from the Relativistic Energy-mass equivalence. (As Hitmouse stated!) It comes about because the conservation of mass didn't work in special relativity and therefore it was required to 'fold in' the conservation of Energy also to make it work. Thus one finds that the universe can convert mass to energy and energy to mass.

The full term is

Now if we take the frame of reference of any individual particle, called the centre of mass frame I think, it is stationary therefore it has zero velocity and p=0 and the familiar E = m_0 c ^2 drops out. However if we look at the particle from another frame of reference - say a moving frame - then we also need, in order to be exact, to add the momentum term.

At no point have I talked about any other particle or field to derive this equation thus it is not a potential energy. Or at least potential energy as defined by physics.

I see where you are coming from, I think....but because energy and mass are equivalent and these are conserved, in a closed system the value of 'E' is a constant. On the other hand, a particle in a field can vary the total energy of the system by moving in the field, and this is what we mean by potential energy.

 

[hitmouse]

No, that's why I said it doesn't describe kinetic energy, what it describes is the potential energy available if it's completely converted to energy.

Apologies for misreading your post. What Venusian Broon said about potential energy, though. By textbook definition, a bit different to the energy implied by E:M equivalence.

 

[Vertigo]

Potential energy is the energy of a particle that it possesses because of it's position relative to other particles. Usually we think of a particle and it's relationship to a field, where the field has been generated by another particle. e.g. gravitational field and mass.

E=mc^2 is a truncated term that comes from the Relativistic Energy-mass equivalence. (As Hitmouse stated!) It comes about because the conservation of mass didn't work in special relativity and therefore it was required to 'fold in' the conservation of Energy also to make it work. Thus one finds that the universe can convert mass to energy and energy to mass.

The full term is

Now if we take the frame of reference of any individual particle, called the centre of mass frame I think, it is stationary therefore it has zero velocity and p=0 and the familiar E = m_0 c ^2 drops out. However if we look at the particle from another frame of reference - say a moving frame - then we also need, in order to be exact, to add the momentum term.

At no point have I talked about any other particle or field to derive this equation thus it is not a potential energy. Or at least potential energy as defined by physics.

I see where you are coming from, I think....but because energy and mass are equivalent and these are conserved, in a closed system the value of 'E' is a constant. On the other hand, a particle in a field can vary the total energy of the system by moving in the field, and this is what we mean by potential energy.

Apologies for misreading your post. What Venusian Broon said about potential energy, though. By textbook definition, a bit different to the energy implied by E:M equivalence.

Oh I agree, I was playing on words a little but my main point was to contradict an assertion earlier in the thread that described e=mc^2 as kinetic energy

 

[BAYLOR]

Perhaps in a billion years we will build giant space generational habitats that can travel between star systems. Maybe we can build enough them movie Earths entire population out of harms way.